The extendr project: Integrating R and Rust

class: center, middle, title-slide

# The extendr project: Integrating R and Rust
### Claus O. Wilke
### last updated: 2021-04-20

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.headline-text[
# How did I get myself<br>into this mess?
]

???

[Photo by Rene Asmussen from Pexels](https://www.pexels.com/photo/house-renovation-3990359/)

---

## ggtext: Styling of ggplot text elements with inline CSS

.xtiny-font.pull-left[

```r
library(ggtext)

colors <- c(
  Adelie = "#FFAF6F", Chinstrap = "#B455F3",
  Gentoo = "#4CA4A4"
)

penguins %>%
  mutate(
    style = glue("color: {colors[species]};"),
    facet_label = glue(
"<strong style='{style}'>{species}</strong>"
  )) %>% ggplot() +
  aes(x = flipper_length_mm, y = body_mass_g) + 
  geom_point(aes(color = species)) +
  scale_color_manual(
    values = colors, guide = "none"
  ) +
  facet_wrap(~facet_label) +
  theme_bw() + theme(
    strip.text = element_markdown(size = rel(1)),
    strip.background = element_blank()
  )
```
]

.xtiny-font.pull-right[
![](data:image/png;base64,#Wilke_NY_meetup_Apr_2021_files/figure-html/penguins-ggtext-out-1.svg)

https://wilkelab.org/ggtext/
]

---

## But I really want to be able to use CSS selectors

.xtiny-font.pull-left[

```r
css <- "
.Adelie    { background-color: #FFAF6F; 
             color: #303030; }
.Chinstrap { background-color: #B455F3; 
             color: #F0F0F0; }
.Gentoo    { background-color: #4CA4A4;
             color: #F0F0F0; }

p { text-align: center; padding-top: 2px;
    font-weight: bold;}"
```
]

.xtiny-font.pull-right[

```r
penguins %>%
  mutate(
    facet_label = glue(
"<p class = '{species}'>{species}</p>"
  )) %>% ggplot() +
  aes(x = flipper_length_mm, y = body_mass_g) + 
  geom_point(aes(color = species)) +
  scale_color_manual(
    values = colors, guide = "none"
  ) +
  facet_wrap(~facet_label) +
  theme_bw() + theme(
    strip.text = element_html(
      css = css, size = rel(1)
    ),
    strip.background = element_blank()
  )
```

https://clauswilke.com/sinab/
]

---

## But I really want to be able to use CSS selectors

.xtiny-font.pull-left[

p { text-align: center; padding-top: 2px;
    font-weight: bold;}"
```

![](data:image/png;base64,#Wilke_NY_meetup_Apr_2021_files/figure-html/penguins-sinab-out-1.svg)
]

.xtiny-font.pull-right[

https://clauswilke.com/sinab/
]

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---

## Benefits of Rust

- Compiled, performance of C

- Compiler protects against undefined behavior

- Modern abstractions: generics, containers, functional programming

- Powerful macro programming language

- Integrated build environment, dependency management

- Built-in framework for unit tests

- Built-in framework for documentation and distribution

## but ...

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# <br>Learning Rust can be<br>a steep climb

???

Photo credit:  
[Tommy Lisbin](https://unsplash.com/@tlisbin)  
https://unsplash.com/photos/_37crDvsAqE

---

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# <br>It's just like C++?

---

## A simple Rust program: Multiples of 3 and 5

.tiny-font[
```rust
fn main() {
    let x = 1..;  // all integers from 1 to infininity
    
    let y:Vec<_> = x
        .into_iter() // convert to iterator
        .filter(     // filter out numbers divisible by 3 or 5
            |z| z % 3 == 0 || z % 5 == 0
        )
        .take(10)    // keep the first 10
        .collect();  // collect into vector
        
    println!("{:?}", y);
    //println!("{:?}", x);
}
```
]

Try it on the [Rust Playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=ae012e466928d5adbb68b86ac7ffb43f)

---

## Fizzbuzz in Rust

.tiny-font[
```rust
fn buzz(i: i32) -> (i32, Option<&'static str>) {
    match (i % 3, i % 5) {
        (0, 0) => (i, Some("FizzBuzz")),
        (0, _) => (i, Some("Fizz")),
        (_, 0) => (i, Some("Buzz")),
        (_, _) => (i, None),
    }
}

fn main() {
    for i in 1..16 {
        println!("{:?}", buzz(i));
    }
}
```
]

Try it on the [Rust Playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=00850f854bfb5a8248a9b506358662a2)

---

## Combining the two previous examples

.xtiny-font[
```rust
fn buzz(i: i32) -> (i32, Option<&'static str>) {
    match (i % 3, i % 5) {
        (0, 0) => (i, Some("FizzBuzz")),
        (0, _) => (i, Some("Fizz")),
        (_, 0) => (i, Some("Buzz")),
        (_, _) => (i, None),
    }
}

fn main() {
    let y: Vec<_> = (1..)
        .into_iter() // convert to iterator
        .map(buzz)   // run `buzz()` over each integer
        .filter(     // retain interesting cases
            |z| z.1.is_some(),
        )
        .take(10)    // keep the first 10
        .collect();  // collect into vector

println!("{:?}", y);
}
```
]

Try it on the [Rust Playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=0984382148c0680b31bdf024981c0e7f)

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.text-on-image[
## <br><br><br>How do we get Rust and R to talk to each other?
]

???

Photo credit:  
[Christina @ wocintechchat.com](https://unsplash.com/@wocintechchat)  
https://unsplash.com/photos/HocFQHhGjDE

---

## The extendr project: Rust crate and R package

<img src = "data:image/png;base64,#resources/extendr-logo.svg", width = 20%, style = "vertical-align: middle;" /> **extendr:** Rust crate providing bindings to R

<img src = "data:image/png;base64,#resources/rextendr-hexlogo.svg", width = 15%, style = "vertical-align: middle; margin-left: 2.5%; margin-right: 2.5%;" /> **rextendr:** R package providing support for the extendr crate

???

The extendr logo and hexlogo are distributed under the terms of the [Creative Commons Attribution-ShareAlike 4.0 International license](https://creativecommons.org/licenses/by-sa/4.0/) (CC-BY-SA 4.0).

[The R logo](https://www.r-project.org/logo/) by The R Foundation is licensed under [CC-BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/).

[The Rust logo](https://github.com/rust-lang/rust-artwork) by Rust Foundation is licensed under [CC-BY 4.0](https://creativecommons.org/licenses/by/4.0/).

---

## Partners in crime

<img src = "data:image/png;base64,#https://avatars.githubusercontent.com/u/1556316", width = "15%" /> &nbsp;&nbsp;&nbsp; [Andy Thomason](https://github.com/andy-thomason)

<img src = "data:image/png;base64,#https://avatars.githubusercontent.com/u/8782986", width = "10%" /> &nbsp;&nbsp;&nbsp; [Ilia Kosenkov](https://github.com/Ilia-Kosenkov)
<img src = "data:image/png;base64,#https://avatars.githubusercontent.com/u/1978793", width = "10%", style = "margin-left: .5in;"/> &nbsp;&nbsp;&nbsp; [Hiroaki Yutani](https://github.com/yutannihilation)
<img src = "https://avatars.githubusercontent.com/u/4706822
", width = "10%", style = "margin-left: .5in;"/> &nbsp;&nbsp;&nbsp; [Daniel Falbel](https://github.com/dfalbel)

and [several others](https://github.com/extendr/extendr/graphs/contributors)

---

.move-down[
## You don't need **rextendr** to write R packages using Rust
]

(But it'll make your life easier; think of it as **devtools** for **extendr**)

---

## Calling Rust code from R: functions

.pull-left[

**Rust code**

.tiny-font[

```rust
use extendr_api::prelude::*;

#[extendr]
fn add_float(x: f64, y: f64) -> f64 {
    x + y
}
```
]]

.pull-right[

**R code**

.tiny-font[

```r
add_float(34.5, 64.2)
```

```
[1] 98.7
```
]]

---

## Calling Rust code from R: objects

.pull-left[

**Rust code**

.tiny-font[

```rust
struct Counter {
    n: i32,
}

#[extendr]
impl Counter {
    fn new() -> Self { Self { n: 0 } }
    
    fn increment(&mut self) { self.n += 1; }
    
    fn get(&self) -> i32 { self.n }
}
```
]]

.pull-right[

**R code**

.tiny-font[

```r
x <- Counter$new()
x$get()
```

```
[1] 0
```

```r
x$increment()
x$increment()
x$get()
```

```
[1] 2
```
]]

---

## Calling R code from Rust

.tiny-font[

```rust
let data = R!(tibble::tibble(x = 1:5, y = 6:10))?;

data
```

```
# A tibble: 5 x 2
      x     y
  <int> <int>
1     1     6
2     2     7
3     3     8
4     4     9
5     5    10
```
]

.absolute-bottom-right.small-font[
Note: Valid for extendr 0.2. API will change somewhat with the next extendr release.
]

---

## Calling R code from Rust

.tiny-font[

```rust
let data = R!(tibble::tibble(x = 1:5, y = 6:10))?;

rprintln!("Contents of data: {:?}", data);
```

```
Contents of data: r!(List([r!([1, 2, 3, 4, 5]), r!([6, 7, 8, 9, 10])]))
```
]

.absolute-bottom-right.small-font[
Note: Valid for extendr 0.2. API will change somewhat with the next extendr release.
]

---

## Calling R code from Rust

.tiny-font[

```rust
let data = R!(tibble::tibble(x = 1:5, y = 6:10))?;

let iter = data.as_named_list_iter().ok_or("expected a list")?;
rprintln!("Contents of iter: {:?}", iter);
```

```
Contents of iter: Zip { a: ["x", "y"], b: [r!([1, 2, 3, 4, 5]), r!([6, 7, 8, 9, 10])] }
```
]

.absolute-bottom-right.small-font[
Note: Valid for extendr 0.2. API will change somewhat with the next extendr release.
]

---

## Calling R code from Rust

.tiny-font[

```rust
let data = R!(tibble::tibble(x = 1:5, y = 6:10))?;

let iter = data.as_named_list_iter().ok_or("expected a list")?;
rprintln!("Individual data columns:");
for column in iter {
    rprintln!("Column {:}: {:?}", column.0, column.1);
};
```

```
Individual data columns:
Column x: r!([1, 2, 3, 4, 5])
Column y: r!([6, 7, 8, 9, 10])
```
]

.absolute-bottom-right.small-font[
Note: Valid for extendr 0.2. API will change somewhat with the next extendr release.
]

---

## Explore Rust code from an R session with **rextendr**

.tiny-font[

```r
library(rextendr)

# create a Rust function
rust_function("fn add(a:f64, b:f64) -> f64 { a + b }")

# call it from R
add(2.5, 4.7)
```

```
[1] 7.2
```
]

---

## Embed compiled Rust code in your RMarkdown

.pull-left[

**RMarkdown input**

.tiny-font[
````markdown
```{extendr}
let x = 5;
let y = 7;
let z = x*y;

assert_eq!(z, 35);
```
````
]]

.pull-right[
**Rendered output**

.tiny-font[

```rust
let x = 5;
let y = 7;
let z = x*y;

assert_eq!(z, 35);
```
]]

How do we know this actually got compiled and run?

---

## Embed compiled Rust code in your RMarkdown

.pull-left[

**RMarkdown input**

.tiny-font[
````markdown
```{extendr}
let x = 5;
let y = 7;
let z = x*y;

assert_eq!(z, 35);

// No semicolon,
// value is returned to R
z
```
````
]]

.pull-right[
**Rendered output**

.tiny-font[

```rust
let x = 5;
let y = 7;
let z = x*y;

assert_eq!(z, 35);

// No semicolon,
// value is returned to R
z
```

```
[1] 35
```
]]

---

## Chaining multiple Rust chunks together

.pull-left[

**RMarkdown input**

.tiny-font[
````markdown
Define variable `x`:

```{extendr A, eval = FALSE}
let x = 1;
```

Define variable `y`:

```{extendr B, eval = FALSE}
let y = 2;
```

Print:

```{extendr out, preamble = c("A", "B")}
rprintln!("x = {}, y = {}", x, y);
```
````
]]

.pull-right[

**Rendered output**

.tiny-font[

Define variable `x`:

```rust
let x = 1;
```

Define variable `y`:

```rust
let y = 2;
```

Print:

```rust
rprintln!("x = {}, y = {}", x, y);
```

```
x = 1, y = 2
```
]]

---

background-image: url("data:image/png;base64,#https://images.pexels.com/photos/37730/sunset-boat-sea-ship-37730.jpeg")
background-size: cover
class: center

.doublespacing.text-on-image[
## “Most people overestimate what they can do in one year and underestimate what they can do in ten years.”<br><span class = "fill-to-right">— Bill Gates<span>
]

???

Photo source here
https://www.pexels.com/photo/sunset-ship-boat-sea-37730/

---

## Resources

- **extendr**
  - [Release on crates.io](https://crates.io/crates/extendr-api)
  - [Documentation (released version)](https://docs.rs/extendr-api/)
  - [Documentation (in development)](https://extendr.github.io/extendr/extendr_api/)
  - [Source repository](https://github.com/extendr/extendr)

- **rextendr**
  - Release on CRAN: coming soon
  - [Pakackge website](https://extendr.github.io/rextendr/)
  - [Source repository](https://github.com/extendr/rextendr)